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GROUND-BASED SOLAR RESEARCH: AN ASSESSMENT AND STRATEGY FOR THE FUTURE Chapter 3 Strategy for the Future Taking into account the principal scientific problems confronting contemporary solar physics and the key roles of ground-based research in addressing those problems (as outlined in Chapter 1), and based on its assessment of current and approved ground-based programs and capabilities (as summarized in Chapter 2), the task group concluded that while there is great strength in the current ground-based solar research program, it is nevertheless fragile. Specifically, there is an urgent need to develop a coherent strategy for ground-based research that would address the following issues: Aging national facilities; Limited capabilities to pursue the most important scientific problems; Concerns about the health of the research community, especially in academia; and The need for a workable plan to effectively integrate the diverse pieces of ground-based solar research into a synergistic whole. The task group concluded that such a strategy can be built around the three elements considered in Chapter 2: (1) major observing facilities; (2) data, theory, and modeling; and (3) people, programs and institutions. Furthermore, the task group believes that the highest priority within the strategy should be accorded to major observing facilities. This is so for several reasons. First, new observing facilities are required to address the major scientific questions in solar research. Second, new facilities are needed to replace certain of the aging facilities now in operation. Third, but especially importantly, major new facilities will constitute the most effective way to attract and engage the next generation of outstanding researchers, who will bring vigor and momentum to ground-based solar research in the United States. Anecdotally, with respect to the third reason, what the task group likens to the “field of dreams” effect (“if you build it, they will come”) appears to have occurred in the growing helioseismology research community—a result of the development of the Global Oscillations Network Group (GONG) and its space-based counterpart, the Solar Oscillations Investigation (SOI), which uses the Michelson Doppler Imager (MDI) instrument on the Solar and Heliospheric Observatory (SOHO) satellite. GONG officials estimate that approximately one-third of the PhDs awarded recently in solar physics have been in helioseismology, an increase of at least a factor often during the past decade. In this same period, participation by helioseismologists in the annual meeting of the Solar Physics Division of the American Astronomical Society has increased from approximately 30 to more than 180 participants. Furthermore, scientists in related areas of astrophysics are now attending meetings to gain insights into research problems in their particular fields, and scientists from other disciplines are bringing their techniques for application in studies of the Sun. From 1987 to June 1998, GONG-related work was described in approximately 160 journal papers; during the same period, more such papers were authored by scientists not affiliated with the National Solar Observatory (NSO). For example, of the 56 GONG-related papers published as of mid-1998, 43 had non-NSO lead authors.
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GROUND-BASED SOLAR RESEARCH: AN ASSESSMENT AND STRATEGY FOR THE FUTURE Although helioseismology may be somewhat unique in stimulating strong connections among researchers engaged in observation, theory, and modeling, the task group believes that the GONG and SOI experience illustrates the important point that scientists direct their research to interesting, well-posed problems involving opportunities to make a significant contribution. RECOMMENDATIONS REGARDING FACILITIES The task group believes that the best scientific strategy for upgrading and constructing major observing facilities is represented by the following four projects, which are presented in order of priority. SOLIS Recommendation 1: Complete fabrication of the SOLIS facility over the next 3 years, operate it at an appropriate site, and provide funding for U.S. scientists for data analyses. The Synoptic Optical Long-term Investigation of the Sun (SOLIS) instruments will make optical measurements of solar processes whose study requires sustained observations over periods of years. The program's overarching goal is to test and improve understanding of how and why stars like the Sun exhibit activity. Data from SOLIS will increase the scientific yield from solar spacecraft such as SOHO and TRACE and from ground-based projects such as GONG and RISE, and it is a key element of the proposed Solar Magnetism Initiative (see Appendix J). When it becomes operational, the SOLIS instrument suite will enable the precision monitoring of daily solar activity with whole-disk vector magnetograms, velocitygrams, and spectroheliograms, replacing and greatly surpassing the capability offered by the Kitt Peak Vacuum Telescope and providing opportunities for new, heretofore infeasible, investigations of the Sun. Furthermore, if the facility's proposed state-of-the-art emission line coronagraph were funded, then SOLIS 's capabilities would surpass those of existing coronagraphs at Sac Peak as well as complement the High Altitude Observatory (HAO) white-light coronagraph, the Advanced Coronal Observing System (ACOS) that operates on Mauna Loa, Hawaii. A particular advantage of the proposed SOLIS emission line coronagraph would be its ability to correct accurately for sky brightness, thus providing greatly enhanced sensitivity. The task group endorses the SOLIS project's timely start. SOLIS will be developed and built at Kitt Peak where a suitable building and observing platform are already available, but the SOLIS instruments will be portable, so that once SOLIS is brought into successful operation, it could be moved to a better observing site (perhaps to the superior site anticipated for the Advanced Solar Telescope—see below). With a planned 3-year development and construction schedule, SOLIS will come online near the peak activity (2000-2002) of the current solar cycle.
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GROUND-BASED SOLAR RESEARCH: AN ASSESSMENT AND STRATEGY FOR THE FUTURE GONG Recommendation 2: Upgrade the GONG system by installing appropriate 1024 × 1024 CCD sensors, and operate GONG over a whole solar cycle with funding for data analysis in the United States. The GONG instruments were designed more than a decade ago to provide full-disk Doppler velocity images with a resolution adequate to study globally coherent p-modes. Since then, local helioseismology and investigation of the upper convection zone have become major research areas whose study requires higher angular resolution than is currently possible with this suite of instruments. The original GONG design permits a straightforward upgrade that will provide a resolution limited mostly by atmospheric seeing, with the major changes being the installation of a new charge-coupled device (CCD) camera and a new data collecting and recording system. These upgrades to GONG are underway.1 The upgrade of GONG will quadruple the system's angular resolution to 5 arc-seconds, making it comparable to the 4-arc-second resolution of the SOHO MDI and thus allowing for direct comparison of the data and results obtained with these two facilities. Estimates of the seeing at the GONG sites from the modulation transfer function, measured with the existing instruments, give a typical seeing of 3.5″. The resolution of the upgraded-GONG instrument and the atmospheric seeing, therefore, are well matched. The task group supports the ongoing upgrade of GONG and recommends that the upgraded network come into operation while SOHO is still functioning to provide necessary and crucial cross-calibration and validation of results, and to track as much of solar cycle 23 as possible with this suite of telescopes. Operation through a full solar cycle will establish a complete, precise record of the variations in solar oscillations through all phases of the activity cycle. This precision exploratory logging will be complemented by the precise helioseismological observations from instruments on SOHO (for as long as SOHO operates) and by special studies that may be carried out from ground-based instruments in operation at, for example, Big Bear Lake, Mt. Wilson, and Mauna Loa. Over time scales of years, the upgraded GONG also will operate with a much higher duty cycle (approximately 90%) than MDI, thereby yielding more precise determinations of the global frequencies and more precise information on the higher-order p-modes and their variations in and around active regions. Full-disk magnetograms from the upgraded-GONG also will be obtained every minute, almost 100 times more frequently than the present cadence of the full-disk MDI magnetograms. The highest-resolution MDI observations have a spatial resolution of 1.2 arc-seconds, but only over a limited field of view. Such observations are ideal for local helioseismology but do not give the global picture of the Sun. The task group emphasizes that the scientific opportunities for the upgraded GONG can be pursued only if competitive research grants are available for the necessary detailed analysis and interpretation of the data. 1 Information about GONG and upgrades to the GONG camera is posted on the World Wide Web at <http://www.gong.noao.edu/helio.html> and <http://helios.tuc.noao.edu/new_camera/new_camera.html>.
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GROUND-BASED SOLAR RESEARCH: AN ASSESSMENT AND STRATEGY FOR THE FUTURE Advanced Solar Telescope Recommendation 3: Develop, construct, and operate a 3- to 4-meter Advanced Solar Telescope (AST). Work toward the AST by: Strengthening the NSO adaptive optics program immediately, including an augmentation in funding of approximately $1.5 million for the next fiscal year; Demonstrating the required adaptive optics (0.1″ or better resolution in visible light at 0.5 microns) on a telescope with an aperture of approximately 1.0 to 1.5 meters; Beginning preliminary design of the 3- to 4-m AST so as to be ready for the final design when the adaptive optics has been convincingly demonstrated; and Carrying on site testing to determine an accessible site with the best available seeing as quickly as possible so as to define the task for the adaptive optics and be ready for construction of the AST. Rationale for the AST The task group believes that development of the instrument it calls the Advanced Solar Telescope is the single most important step that can be undertaken to energize ground-based solar physics programs at both national centers and universities. The scientific challenges and research opportunities summarized in Chapter 1 and described more fully in Appendix D and Appendix H, Appendix I and Appendix J drive this and the task group's other recommendations regarding facilities. The task group thinks that the general behavior of the major phenomenological components of solar activity is being characterized effectively in the ongoing ground-based and space programs. Effective studies of the Sun's internal rotation, circulation, and magnetic fields will be enabled by the upgrade of the GONG network, as well as by instruments on spacecraft. However, scientific understanding of the basic physics of these phenomena is stymied by the inability of existing telescopes, which have 0.3-to 1.0-arc-second resolution, to resolve many aspects of the fundamental magnetic energy release processes that are occurring at scales of approximately 0.1 arc-second or less (75 km or less).2 The best existing observations are sufficient only to demonstrate the existence of the microstructure.3 To obtain the required observations, the task group recommends development of a solar telescope and adaptive optics system capable of providing 0.1″ or better resolution 2 Ingenious and technically sophisticated methods such as speckle interferometry can eliminate the distorting effects of the turbulent atmosphere and allow the reconstruction of monochromatic images close to the diffraction limit (0.2″) of existing telescopes (Denker, C. 1998. Solar Phys. 180:81). However, these methods do not provide real-time image reconstruction, but instead rely on post-observation processing. 3 For example, flares, sunspots, X-ray loops, faculae, and the active regions surrounding sunspots (plages), as well as the microflaring among individual magnetic “fibrils” and small emerging bipoles, have microstructure that evidently plays a crucial role in their puzzling observed behavior. The visible brightness of faculae and plages, together with the UV and X-ray emission, accounts for a major part of the total variation of the solar irradiance, while the microflaring seems to be a major contributor to the coronal heat input responsible for the solar wind, and, in another form, for the X-ray corona.
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GROUND-BASED SOLAR RESEARCH: AN ASSESSMENT AND STRATEGY FOR THE FUTURE in visible light at 0.5 microns (µm). At least half of the light should be within a circle of 0.1″ diameter4 for a telescope with an aperture of 3 to 4 meters for at least some atmospheric conditions. The requirement for diameter is necessary to provide enough photons for high-dispersion spectroscopy at the rapid cadence necessary to follow the variations in the Sun's microactivity. The requirement for resolution is necessary to enable forefront science. The need for high sensitivity to magnetic fields also makes desirable an infrared (IR) capability out to 15 µm. Operating at such long wavelengths with even minimally acceptable resolution also requires a large-aperture telescope. Further, the requirement for IR-capable operation excludes the possibility of a vacuum telescope and requires close control of the seeing within the telescope. A low level of scattered light is also desirable to allow looking into pores and sunspots. The task group has dubbed the instrument with these features the “Advanced Solar Telescope,” or AST. It might also be called the “Solar Microscope” because it would, for the first time, peer into the mysterious world of the active magnetic microstructure. The prospect is as exciting to the theoretician as it is to the observer. Development of Adaptive Optics The critical enabling technology for the Advanced Solar Telescope is adaptive optics—without its successful development there will be no way to study the basic microstructure of the solar activity. The current adaptive optics program at NSO is being carried out in collaboration with a U.S. Air Force team at Sac Peak. The program aims to build an adaptive optics system at the Sacramento Peak Vacuum Tower Telescope (Sac Peak VTT) in the next 2 to 3 years.5 The immediate objective is to convert a low-bandwidth system that senses and corrects low-order atmospheric turbulence and telescope aberrations up to 20 spatial modes to higher-bandwidth operation. The system is also intended to provide a platform for further development of low-order adaptive optics, and ultimately a full atmospheric compensation system for use in solar imaging. The program is currently being funded at approximately $0.5 million/year.6 The task group believes that the present program, which is supported out of the current NSO budget, will not be adequate to complete the final full adaptive optics 4 So that contrast in the image is not washed out, at least half of the light from a distant point source must be concentrated within the full width at half maximum, which is different from the less stringent requirement for the nighttime resolution of two close stars, a case in which the spurious light from each of the two stars is spread broadly over the surrounding dark sky. 5 An initial milestone in the adaptive optics program was recently met with operation at a wavelength of 900 nm using a 20 Zernike mode 97 actuator system and a telescope aperture of 0.76 meters (the size of the VTT window). The system demonstrated the crucial sensing of the incoming solar wavefront and the ability to translate that information rapidly into displacement of the 97 active elements of the plane-correcting mirror. In the next phase, NSO staff propose to increase the 25-Hz system bandwidth and to develop an 80 Zernike mode system to correct the VTT down to 500 nm for median seeing. Developing the solar wavefront sensor is the key challenge in solar adaptive optics programs as point source sensing targets are never available everywhere on the solar disk. In general, solar wavefront sensing has to be performed using the granulation, an extended, low-contrast, and evolving structure, as its sensing target. (See NOAO Newsletter, No. 56, December 1998, p. 36, available on the World Wide Web at<http://www.noao.edu/noao/noaonews/dec98/node30.html>.) 6 This figure covers salaries and benefits, hardware, and overhead (J. Beckers, director, NSO, personal communication, September 1998).
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GROUND-BASED SOLAR RESEARCH: AN ASSESSMENT AND STRATEGY FOR THE FUTURE system for the AST in a timely fashion. The task group recommends strengthening the NSO adaptive optics program immediately with an immediate and continuing augmentation in funding of approximately $1.5 million for the duration of the project.7 Further, the task group recommends that development of the adaptive optics system for the 3- to 4-meter AST proceed by first demonstrating resolution of 0.1″ or better in visible light on a telescope with an aperture of approximately 1.0 to 1.5 meters. The success of such an adaptive optics system will demonstrate the feasibility of the AST, help to determine its design parameters, and generate reliable cost projections. The 1.5-m McMath-Pierce telescope is the obvious place to carry on the development of the adaptive optics following the success of the current program at the Sac Peak VTT. However, the seeing is relatively poor both inside and outside the McMath-Pierce telescope, although periods of excellent seeing do occur, particularly during the summer months. Developing adaptive optics at this facility will be difficult, and it may be necessary to construct, or borrow time on, a comparable telescope with better seeing conditions. The adaptive optics program will be technically challenging. To be precise, the task is to develop a user-friendly adaptive optics system that can produce 0.1″ images with a duration of 2 seconds and at a cadence of 10 seconds for a period of an hour or more under nominal atmospheric seeing conditions at the site selected for the future AST. It is essential for solar studies that at least half of the power of a distant point source be concentrated in the focused image within the full width at half maximum. These specifications are sufficient, for instance, to produce high-resolution Stokes polarimetry at a signal-to-noise ratio sufficient to do forefront science. Note that an adaptive optics system for visible radiation (500 nm) in a telescope of 1.5 m is sufficient for a 4-m telescope at wavelengths greater than 1.13 µm.8 Observations of the solar surface present somewhat the same problem in contrast as do nighttime observations of faint structure in the disk of a galaxy. For the broad face of the Sun, every point contributes its unwanted point spread function. Therefore, more active elements are required to hold down the spread light, and it has yet to be demonstrated how well this can be done. On the other hand, adaptive optics for solar observations has enough photons available from the field of view itself and, therefore, does not have to grapple with the expensive technical problem of producing a sufficiently bright artificial laser star. The task group is cautiously optimistic about the present line of development. Cost of the AST The development of the AST will be a major undertaking that the task group estimates will cost some $50 million, not including instrumentation. This estimate is based on costs of existing large solar telescopes and three proposed large-aperture 7 With difficulty, NSO is supporting the current adaptive optics effort at a level of approximately $0.5 million/year. The task group believes that a sustained effort of approximately $1.5 million/year will be necessary for timely accomplishment of the goals of the adaptive optics program outlined in the text. Thus, the task group recommends an additional $1.5 million/year for adaptive optics development. 8 Note, too, that the same adaptive optics system does not have to work as fast at 1.13 microns since the time constant for seeing changes is longer by a factor of 2.7.
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GROUND-BASED SOLAR RESEARCH: AN ASSESSMENT AND STRATEGY FOR THE FUTURE telescopes placed on a common 1996 U.S. dollar scale (Table 3.1). These data were taken from information compiled by J. Beckers, D. Rabin, and other NSO staff members and from a draft document on LEST.9 The costs of instrumentation (where specified) and adaptive optics are shown as separate entries and have been broken out of the quoted cost estimates of the three proposed telescopes; the estimates for CLEAR are shown for two apertures. TABLE 3.1 Solar Telescope Costs (1996 millions U.S.$) Costs Telescope Aperture (m) Telescope Instrumentation Adaptive Optics NSO McMath-Pierce 1.50 30 ...... ....... NSO VTT 0.76 30 ...... ...... LEST original 2.44 43 8.7 8.3 LEST recent 3 25 4.5 3.8 CLEAR* 3 31 4.5 3.1 CLEAR* 4 39 4.5 3.3 * Off-axis telescope, noncoronographic (mirror not superpolished). Development of a new site is estimated to cost ~$6M, including purchase of property and payments for roads and utilities, site preparation, data lines, and nontelescope construction costs. The estimates given in Table 3.1 can also be checked through comparison with costs for nighttime telescopes. For example, the cost of the 4-meter SOAR10 telescope—a conventional design at a developed site—is projected to be $27M with minimal instrumentation.11 A flagship solar telescope such as the AST will cost more than a nighttime facility of comparable aperture. A cost estimate for the AST should also include a realistic, defined complement of first-light instrumentation. The task group believes that the effectiveness of the AST in addressing the scientific challenge of understanding solar activity will depend on both designing an adequate adaptive optics system and securing an adequate complement of supporting instruments (for example, cameras and spectrographs). In addition, adequate support for operations, observations, data analysis, and theoretical interpretation is essential for effective utilization of the instrumented AST. Achieving the scientific payoff of the AST investment will require a full-up approach to the project. The AST is the ground-based gateway to an effective observational assault on understanding the activity of the Sun. 9 Jacques Beckers, “Summary of Feasibility Study of CLEAR,” presentation to the task group, July 29, 1997, and O. Engvold, “A Simplified, Alternative Design of the LEST,” June 21, 1996. Note that the exchange rate for the Swedish Krona was about 6.63 SEK/U.S.$ at the time the LEST paper was written. Information on LEST can be found on the World Wide Web at <http://www.uio.no/~zhang/index.html>. 10 The Southern Observatory for Astrophysical Research (SOAR) is an international consortium to build and operate a high-performance 4-meter-aperture astronomical observatory on Cerro Pachon, Chile. Information on SOAR is available on the World Wide Web at< http://ctios6.ctio.noao.edu/soar/>. 11 The $27M figure represents the agreed-to cost for designing, building, and getting to first light for the SOAR telescope. The cost breakdown is $24M for the telescope and $3M for a minimal suite of focal plane instruments (administrative staff, NOAO, personal communication, 1998).
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GROUND-BASED SOLAR RESEARCH: AN ASSESSMENT AND STRATEGY FOR THE FUTURE Siting of the AST The AST must be located at a site with the best available atmospheric seeing—the better the seeing and the more effective the control of the seeing within the telescope, the easier and less costly will be the ultimate achievement of the necessary telescopic resolution of 0.1″ or better in visible light. (Driving the cost of the adaptive optics system are the number and control of the active elements and the quality of the atmospheric seeing.) The task group believes that site study, selection, and development should begin soon and progress rapidly, because the actual quality of seeing will determine the technical challenges. The NSO staff is currently doing some preliminary site testing, while carrying on the development of the adaptive optics at the Sac Peak VTT. They have also constructed a mock-up of an open telescope to study the internal seeing problem, experimenting with, for example, temperature control and air flow. The remarkable performance of the Dutch open tower telescope on the Canary Islands indicates that a simple flow of air over the primary mirror goes a long way toward controlling the internal seeing.12 A secondary criterion for site selection should be convenient access by scientists and technicians. The task group believes that this criterion weighs in favor of a U.S. site, and that a foreign site should be considered only if a detailed search turns up no U.S. site with seeing sufficiently good to ensure successful operation of AST adaptive optics. However, if international partners commit to a substantial share of the cost of the AST, they should help to establish the criteria for site selection. A third criterion is the cost of site development and operations. International Collaboration and the AST It is desirable to develop international collaboration between the adaptive optics groups at the NSO and the groups working at the solar telescopes in the Canary Islands and elsewhere. For example, funding was approved recently for a 1-meter upgrade to the Swedish Vacuum Solar Tower (SVST) at La Palma, with plans to develop an adaptive optics system. The task group expects that a successful AST project will excite the active interest of the entire solar community, both domestic and international, and it encourages the NSO to explore international collaboration in the design and instrumentation of the AST. The task group sees the AST together with the upgraded GONG and the recently approved SOLIS instrument array as the cornerstones of a program that will offer the international solar physics community access to the best ground-based solar observing facilities in the world. 12 The open tower telescope (OTT), recently assembled, is an innovative design aiming at observations of the Sun with high angular resolution at relatively low cost. It consists of an open-framework tower of 15 m, supporting an open-construction telescope. The telescope is not protected by a domelike enclosure; instead, the open structure allows the free wind flow to keep the air within the instrument and in its vicinity thermally homogeneous, thus ensuring the best possible image quality. The price paid is that the OTT has to be exceedingly stiff to withstand the highly variable wind load. Moreover, the design has to include thermal control of the light path in the telescope. Information about the OTT is available online at <http://www.stw.nl/projecten/U/uns2428.html>.
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GROUND-BASED SOLAR RESEARCH: AN ASSESSMENT AND STRATEGY FOR THE FUTURE Timetable for AST Development The timetable for completion of the AST will be paced by the adaptive optics development and demonstration. The current program, which is being carried out at the Sac Peak VTT, aims to have a limited system for sensing and correcting atmospheric turbulence and the slowly varying aberrations in the optical system of the VTT by approximately the beginning of 2001.13 The task group believes that the recommended adaptive optics demonstration it envisages might be accomplished in approximately 3 to 4 years (2002-2003), assuming that the preliminary optics development proves itself and assuming that the recommended level of funding ($1.5 million/year) is made available during this time. Preliminary design work for the AST can proceed in parallel with the adaptive optics work; however, the final decisions on the design and funding of the ultimate AST should be contingent on experience and demonstrated success with the adaptive optics and control of internal seeing as they would perform at the future site. Making reasonable estimates for the time to pass through Phase A, preliminary design, Phase B, concept definition, and Phases C and D, design, development, and fabrication (with some 2 years for construction) implies a ready date for the AST of perhaps 2007-2009. Exploratory Development—FASR Recommendation 4: Begin exploratory development of a high-resolution, frequency-agile solar radio telescope (FASR), using existing radio observatories to demonstrate its scientific potential. A FASR would provide unique diagnostics of solar flare plasmas, as well as maps of magnetic fields over surfaces of constant density in active regions. Equally important would be its unique ability to detect and locate the myriads of microflares. The task group recommends exploratory work to establish the scientific potential of a FASR, noting also that there is international interest in proceeding with a study of the optimum FASR design. The task group points out that a FASR could be developed at relatively low cost on a cooperative international basis using existing large antennas, so that the telescope could be up and running in time for the solar maximum in approximately 2011. Compared to the capabilities of the existing dedicated solar radio facilities discussed in Chapter 2—the French Nançay Radioheliograph and the Japanese Nobeyama Solar Radio Telescope —the FASR concept presented to the task group (Appendix E) would have more than 800 frequencies in the range from 500 MHz to 26 GHz. The FASR's higher frequencies would give correspondingly better resolution than the Nançay radiograph, and its larger number of dishes would result in better image quality. The FASR would also improve on the capabilities of the Nobeyama facility in its frequency coverage, spatial resolution, and image quality. 13 As noted above, the initial 20 Zernike mode 97 actuator adaptive optics system for the Sac Peak VTT was successfully demonstrated in late 1998.
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GROUND-BASED SOLAR RESEARCH: AN ASSESSMENT AND STRATEGY FOR THE FUTURE RECOMMENDATIONS REGARDING DATA, PEOPLE, PROGRAMS, AND INSTITUTIONS The four recommendations given above all relate to priority actions for major observing facilities; they are intended to address concerns about major facilities cited in Chapter 2. The recommendations below focus on addressing the issues that emerge from Chapter 2 in the two other major elements of the U.S. ground-based solar research program, which are (1) data, theory, and modeling and (2) people, programs, and institutions. They are presented in no particular order. Toward a New National Solar Observatory Recommendation 5: Facilitate efficient and timely development and utilization of the AST through enhancements to the management and organization of the NSO. The task group elected to present recommendations regarding the management and operational structure of the NSO first in this portion of the strategy because they all pertain to implementation of the highest-priority recommendation for a major new observing facility, the AST. The task group expects that the National Solar Observatory will manage the recommended ground-based solar optical facilities—the SOLIS instrument suite, the upgraded GONG, and eventually the Advanced Solar Telescope. These facilities will be the cornerstone of a new National Solar Observatory that would be the premier institution in the world for ground-based optical and infrared observations of the Sun. Scientists using the facilities at the new NSO would be able for the first time to study the Sun's basic microscopic activity, its changing surface magnetic and flow patterns, and its subsurfac motions and magnetic fields. Recommendation 5a: Consolidate the NSO science, engineering, and operations site when the AST is operational. The recommended facilities for ground-based solar optical astronomy are intended to replace the existing NSO solar telescopes at Sacramento Peak and Kitt Peak. However, neither the Sac Peak site nor the Kitt Peak site provides the optimal seeing necessary to achieve the high angular resolution that is essential to the success of the AST. Although solar astronomers do not yet know where the optimal sites are located, they do know that better sites for solar astronomy exist, for example in the Canary Islands and at Big Bear Lake in southern California. It may be desirable for NSO to install the SOLIS facility at the same site as the AST. If a scientifically suitable U.S. site is identified, then there are advantages to be gained if the NSO consolidates its offices at a single site, conveniently located near the AST. The Sac Peak and Kitt Peak sites would be abandoned at about the time that the AST becomes operational with a workable complement of instruments. The primary criterion in selecting the site of the NSO's scientific headquarters must be location at a place that is attractive to excellent scientists and technical staff. The secondary criterion is that it be located at a convenient distance from the AST site and near a supportive academic environment. In the likely event that this means NSO
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GROUND-BASED SOLAR RESEARCH: AN ASSESSMENT AND STRATEGY FOR THE FUTURE moving out of the present Tucson offices, financial costs (for example, for real-estate, relocation, and possible nonfederal capital contributions) and a variety of issues related to managing the transition to a new site would have to be studied in detail. Another issue for the future relates to coronal observations. The NSO would be without a coronagraph should Sac Peak be closed.14 Coronal observations would still be provided by HAO's white-light coronagraph, ACOS, and from space observations, for example, those from SOHO and TRACE. However, data transmission, if nothing else, decrees that space observations cannot match the spatial and spectral resolution (and the low scattered light) of a technically advanced ground-based coronagraph such as ACOS. Given these circumstances, the task group believes that the best and least expensive way to restore the lost capabilities would be the inclusion of the complementary emission line coronagraphic instrument in the SOLIS array, which would have great sensitivity arising from subtraction of sky brightness. The task group is aware that the AST will not replace all the scientific performance of all the instruments on Sac Peak, or of the McMath telescope on Kitt Peak—some valuable observing modes will be lost. However, the task group believes that the loss of some of these capabilities is a price that U.S. solar astronomers must pay to keep operating costs under control. The recommendation that NSO consolidate its primary facilities at a new site raises the opportunity for NSO to consolidate its scientific and technical operations, a move that the task group believes will strengthen NSO as a center for U.S. solar astronomy. Recommendation 5b: Establish an independent management council of the NOAO management organization to represent solar research, thereby recognizing the unique requirements for a program in ground-based studies of the Sun and placing such a program on an equal footing with the other major initiatives of NOAO. For some time, it has been widely recognized that the current organization of the NSO is not optimally matched to carrying out its mission of developing and maintaining the principal ground-based solar physics facilities in the United States. The split of NSO into two widely separated staff and observing sites (Kitt Peak/Tucson and Sac Peak) has led to a lack of synergy and a divergence of scientific and administrative goals that have proved difficult to resolve. The marriage between the nighttime-astronomy-dominated NOAO and the daytime NSO has been challenged by natural divergences of long-term interests, which have been exacerbated by the current constrained fiscal climate. As a result of these two problems, NOAO and NSO have not been able to take full advantage of economies of scale, which might be expected to flow from combined operations. The task group has been advised by the NOAO-NSO management and many of the NSO staff that both organizations would probably operate more smoothly if they were fully independent, and the task group agrees. The prospect of replacing the Sac Peak and Kitt Peak facilities with new facilities sets the stage for reconstituting the present NSO into a new, unified, and fully autonomous NSO, which will be able to 14 The Evans Solar Facility at Sac Peak provides two 40-cm coronagraphs on a common spar, as well as a coelostat. These two coronagraphs are the largest in the United States and the best instrumented in the world.
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GROUND-BASED SOLAR RESEARCH: AN ASSESSMENT AND STRATEGY FOR THE FUTURE provide renewed scientific leadership for ground-based solar astronomy in the United States. NSO and NOAO have already moved in this direction by having the director of NSO report directly to the Association of Universities for Research in Astronomy (AURA) on issues involving NSO scientific strategy and management. An appropriate next step toward NSO autonomy will be for NSO and NOAO to work rapidly toward a full separation of operating budgets. Of course, both organizations will share resources as long as they share the same physical facilities. However, they should move quickly to establish separate accounting systems that prorate the costs of all shared resources in as much detail as possible, moving from there to eventual complete operational autonomy for the NSO. Now is a good time for NSF to recognize the progress toward separate operations by encouraging establishment of a solar council to represent the NSO on an equal footing with the Gemini project and the nighttime NOAO operations, each with its own council. The present solar subcommittee would be dissolved upon establishment of the solar council. Recommendation 5c: Establish an advisory committee to the NSO director that would include leading solar physicists from NSO, HAO, universities, NASA, DOD, NOAA, and U.S. and international research partners. The complexity of the development and construction of the AST, combined with relocation to a final site, is of such magnitude, affecting the entire solar physics program of the United States, that a general advisory group should be set up to assist the director of the NSO in evaluating the many problems and questions that will arise over the coming years. The advisory group would provide input on plans for the new NSO and its facilities, including options for international collaborations. Recommendation 5d: Foster communication within the solar physics community by considering creation of an NSO national fellowship program, perhaps structured along the lines of the visiting scientist program that has been in place for many years at HAO. The principal source of openly available observational data acquired from ground-based instrumentation is the NSO. Therefore, strong coupling is essential between the NSO and the university and institutional community, where much potential data analysis and theoretical effort resides. Thus, for instance, it would be mutually advantageous for the new NSO headquarters to be located at or close to a supportive university. The task group also believes that NSO would benefit from a fellowship program. It envisions a program that would support a small number of researchers and postdoctoral fellows, more or less along the lines that the High Altitude Observatory has pursued for many years, while continuing the student outreach and workshops that are part of the program at Sac Peak. Each fellow would have a primary affiliation with a university while spending a significant fraction of time at NSO. The costs of such a program might be several hundred thousand dollars per year.
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GROUND-BASED SOLAR RESEARCH: AN ASSESSMENT AND STRATEGY FOR THE FUTURE People, Programs, and Institutions Recommendation 6: Establish the essential national infrastructure for the effective operation and scientific exploitation of the U.S. solar observing facilities. In addition to an adequate complement of supporting instruments, the success of programs such as SOLIS, the upgrade of GONG, and the AST rests on the availability of adequate funds for data analysis, modeling, and basic theoretical investigations. Plans for this intellectual infrastucture should be incorporated at the start of new projects. The task group notes the importance of a balanced NSF approach to facility development and scientific grant support for the optimum long-term handling of solar research. This requires NSF research grants for individual solar scientists in universities, institutes, and observatories, as well as active communication and coordination between the centers (NSO and HAO), agencies (NSF, NASA, DOD, and NOAA), and the national infrastructure of universities, observatories, and institutes. The task group believes that the magnitude of the grants program for individual researchers should be commensurate with the funding of the centers. Centers and/or institutional consortia can play an important role in facilitating the integration of observation and theory and the synthesis of new physical models via implementation of “critical-mass ”-size programs of research. An example is the Solar Magnetism Initiative (SMI), a community-based proposal to the NSF for an integrated study of solar magnetism and variability (see Appendix J). The scientific objective of the program is to establish the feasibility of solar activity forecasting by providing the scientific prerequisites for such forecasting. SMI programs will be designed to: Identify and understand the physical processes that control how magnetic fields are generated in the solar interior, rise to the surface, and evolve after emergence; Use this understanding to synthesize a new global paradigm for the operation of the solar cycle; and Produce quantitative models relevant to the development of science-based forecasting tools for solar activity and space weather. The observational base for the SMI encompasses the entire array of ground-based, balloon-borne, and spacecraft instruments. In particular, HAO is directly involved with its Advanced Stokes Polarimeter, its Advanced Coronal Observing System at the Mauna Loa Solar Observatory, and the forthcoming SOLIS facility. A second example is SunRISE. As the third part of the Solar Influence program, the SunRISE (Sun's Radiative Input from Sun to Earth) program aims at complementing the space measurements of solar variability by studying the mechanisms of solar variability and climatic impact. In SunRISE, ground-based observations of the Sun and of the variability of other stars are combined with paleoclimate records and theoretical work. The SunRISE program and proposed SMI project, and similar efforts, are essential for exploiting the full potential of modern solar research. Recommendation 7: NSF and NASA should collaborate on development of a distributed data archive with access through the World Wide Web.
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GROUND-BASED SOLAR RESEARCH: AN ASSESSMENT AND STRATEGY FOR THE FUTURE The importance of readily accessible and usable data sets is addressed in Chapter 2. Such access requires easily searchable catalogs, user-friendly access software, and the capacity to handle large volumes of data. Chapter 2 also notes that a number of organizations, both in the United States and abroad, have taken the initiative to preserve and provide data sets online. Acknowledging the importance of providing data to the community, the task group encourages the cooperation of observatories and institutions, especially NSF and NASA, in efforts to archive and ensure access to their data. In fact, the task group believes that provisions for data archiving and distribution should be an integral part of planning for future observing facilities. Finally, the task group notes that many organizations now maintain profusely illustrated interactive sites on the World Wide Web; these are excellent platforms for public outreach and public education.
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GROUND-BASED SOLAR RESEARCH: AN ASSESSMENT AND STRATEGY FOR THE FUTURE Appendixes
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Representative terms from entire chapter: